Page 53 - Grapevine Jan-Feb 2020

Around The Vineyard

Cornell University and the University of California
showed that the three-cornered alfalfa tree hopper
(Spissistilus festinus) is able to transmit the virus
under laboratory and greenhouse conditions. The
three-cornered alfalfa tree hopper insect prefers to
feed in legumes, grasses, and shrubs. However, the
discovery of a potential vector cannot explain the
reason for the sudden discovery and rapid spread
of GRBV in vineyards. While research continues
to determine if other vectors are capable of trans-
mitting GRBV it is obvious that the rapid expansion
of this virus in vineyards was due to unknowingly
propagating and grafting cuttings from infected
vines.

Do We Really Understand GRBV Biology?

Recent work performed at Cornell University
has shown a seasonal and uneven distribution
of GRBV in grapevines. This contrasts the work
performed in my laboratory with samples from
field grown vines. My research program (https://
www.researchgate.net/publication/313858753_
Symptom_Expression_and_Detection_of_
Grapevine_red_blotch_virus_in_Red_and_White_
Fruited_Grape_Varieties) showed that red blotch
virus can be detected from any portion of the vine
in high concentrations. In other words, red blotch
virus can be detected in newly expanded as well as
mature leaves, petioles, lignified or green canes,
as well as cordons and trunks. Further, red blotch
virus was detectable throughout the different sea-
sons of the year in samples collected from known
infected vineyards in California. The discrepancy
might be due to a potential latent period needed
for virus to move and colonize vines.

The Russell Ranch Foundation
Block Virus Status

Keeping important viruses such as the ones that
cause leafroll and red blotch diseases out of pro-
ductive vineyards relies on clean planting stock
programs. In California, the Grapevine Registration
and Certification (R&C) is administered by the
California Department of Food and Agriculture
(CDFA). A Few years ago, a new block with progeny
vines produced with tissue culture and thoroughly
tested using the “Protocol 2010” were planted in
the UC Davis Russell Ranch block. The foundation
block is located in close proximity to research plots

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